The present invention relates generally to lift truck attachments and more particularly to attachments suitable for handling wheeled container chassis and the like.
Container trailer chassis are used to transport large, detachable shipping containers and their contents by road. The containers are detached from the chassis for shipment by rail or ship. Large numbers of empty container chassis are stored in storage areas at or near ship and rail terminals when not in use. However, the storage of such chassis is a problem because of their large size and bulky shape and because storage space is often scarce. Moving the chassis within the storage area or to and from loading points can also be a problem because of the lack of maneuvering space available for tractor vehicles and the typically disorganized manner in which the trailers are stored.
It has been suggested that chassis may be stored space efficiently in an upright position in storage racks, such as the storage rack shown in copending application Ser. No. 429,039, filed Sept. 30, 1982, now U.S. Pat. No. 4,493,421. The problem with this storage method, however, is that prior clamping apparatus and attachments for lift trucks are not suitable for handling chassis for upright storage.
Alternatively, the chassis may be stored in an alternating right-side-up, upside-down vertical stacking arrangement with the rear wheels of adjacent trailers positioned at opposite ends of the stack. Each upside-down chassis is flipped on its back onto a bed of tires using conventional lift truck forks, raised to the desired height and deposited onto a rightside-up chassis. Even with the tire bed, however, damage to the chassis can easily result. Moreover, the operation is relatively time consuming and requires space allocation for the tire bed.
An attachment suitable for efficiently handling chassis for storage in either of the above manners without damaging them must be capable of lifting a horizontal chassis off the ground, turning it 90.degree. to an upright position or 180.degree. to an inverted position, and depositing it gently against an underlying support. Such attachment must be able firmly to grip the large, bulky chassis with no risk of slippage while turning it. Ideally, such an attachment should be usable with conventional lift trucks. Such an attachment should also be capable of transporting a chassis in an upright position and with a slim horizontal profile to avoid the aforementioned maneuvering problem.
Examples of prior clamps for lift trucks capable of rotating gripped objects are shown in Weinert, et al. U.S. Pat. No. 4,177,000; Sinclair U.S. Pat. No. 3,896,957; and Overbeck U.S. Pat. No. 2,724,520. All three such clamps have curved clamping jaws specially designed for handling round objects, such as paper rolls and the like, and hence are not adapted for handling container chassis.
Moreover, the clamping jaws of the Sinclair and Weinert, et al. clamps are pivotally supported at common or closely adjacent axes at one end. The opposite clamping ends of the jaws therefore pivot through an arc to clamp the object. Consequently, such jaws are inherently incapable of generating an even clamping force across a relatively wide flat surface, such as the bed of a container chassis, and hence are not suitable for handling chassis.
The Overbeck clamp includes an upper, vertically movable clamping jaw and a stationary lower jaw. Because the upper jaw has a bar/slide type mounting, a ignificant portion of the potential clamping force is lost because of friction between the bar and slide. Consequently, a relatively large, energy inefficient fluid-operated cylinder would be required to handle container chassis. Therefore, the Overbeck clamp is also unsuitable for handling container chassis.
Accordingly, there is a need for a method and apparatus for handling container chassis that enables such chassis to be easily and safely stored and transported.
Therefore, a primary object of the invention is to provide a method and apparatus for handling and storing container trailer chassis.
Another primary object of the invention is to provide a lift truck attachment for handling container chassis that enables them to be stored in various space-efficient arrangements and retrieved therefrom, including vertically on-end and alternating right-side-up, upside-down arrangements.
Another object of the invention is to provide a method and apparatus for storing container chassis in an upright position.
Another object is to provide an apparatus and method for storing container chassis in an alternating right-side-up, upside-down stacking arrangement without damaging the chassis.
Yet another object is to provide an attachment, as aforesaid, with a clamping apparatus capable of applying a clamping force sufficient to prevent slippage of the chassis from its grip.
A further object is to provide an attachment, as aforesaid, in which the clamping apparatus is capable of applying an even clamping force across the full width of the chassis during handling.
A still further object is to provide an attachment, as aforesaid, in which the clamping apparatus includes means for positively preventing slippage of the chassis from its grip.
Another object is to provide an attachment, as aforesaid, capable of turning the chassis through at least 180.degree. in a vertical plane and capable of gripping and releasing the chassis regardless of its orientation and without the need for a side-shaft mechanism.
Still another object is to provide a method and apparatus, as aforesaid, for handling a container chassis by applying a clamping force to the chassis near its center of gravity and from one side of the chassis.